SQL using If Not Null on a Concatenation - Stack Overflow
As @Prdp noted, the answer is RDBMS-specific. What is specific is whether the server treats a zero-length string as being equivalent to NULL, which determines whether concatenating a NULL yields a NULL or not. Generally COALESCE is most concise for PostgreSQL-style empty string handling, and...
sql injection "union select null" - CodeProject
Union select null, null, null, null, null, null, null from information_schema.tables. for a small database containing three tables. this instruction is used in sql injection I tried it and it worked but I didn't really know how it works can somebody help me...
Шпаргалка по SQL инъекциям | DefconRU
(M): SELECT CONCAT(login, password) FROM members. 7. Строки без кавычек Есть несколько
oracle - What is the difference between select count(*) and select...
If one or more null values are eliminated, then a completion condition is raised: warning- null value eliminated in set function. The same rules apply to SQL Server and Sybase too at least. Note: COUNT(1) is the same as COUNT(*) because 1 is a non-nullable expression.
SQL COUNT « Язык запросов SQL
Синтаксис функции COUNT: SELECT COUNT(expression) FROM table WHERE predicates; Функция COUNT принимает один из нескольких параметров
COUNT(*) / Хабр
SELECT FirstName, COUNT(*) FROM Person.Person GROUP BY FirstName. Посмотрел на план запроса и увидел там явно неадекватное значение Estimated number of rows
25 примеров команды SELECT в MySQL | ИТ Блог.
Если вы используете базу данных MySQL, это очень важно, чтобы вы работали комфортно с командной строкой MySQL. На этом уроке мы расскажем, как использовать команду SELECT в MySQL с несколькими...
Ask TOM "Getting multiple counts with a union"
select count(value_x) People from table_a union select count(distinct value_x) People from table_b; We are currently getting: People 24998 23965. We have placed a break on report and computed a sum of count, but that's not really what we want. We would like to see just
MySQL :: MySQL 8.0 Reference Manual :: 12.20.1 Aggregate...
mysql> SELECT COUNT(DISTINCT results) FROM student; In MySQL, you can obtain the number of distinct expression combinations that do not contain
SQL SELECT DISTINCT Statement
SELECT DISTINCT Examples. The following SQL statement selects only the DISTINCT values from the "Country" column in the "Customers" table